When Did Dinosaurs Live?
Dinosaurs dominated Earth for over 165 million years—far longer than humans have existed (about 300,000 years). They lived during the Mesozoic Era, divided into three periods: Triassic, Jurassic, and Cretaceous.
Explore the world of dinosaurs →
The Mesozoic Era (252-66 million years ago)
"The Age of Dinosaurs"
- First dinosaurs appeared (~230 mya)
- Most were small, bipedal
- Shared world with other reptiles
- Supercontinent Pangaea still united
- Hot, dry climate
- Dinosaurs became dominant
- Giant sauropods evolved
- First birds appeared
- Pangaea began breaking apart
- Famous dinosaurs: Allosaurus, Stegosaurus, Brachiosaurus, Diplodocus
- Peak dinosaur diversity
- Flowering plants appeared
- Continents approaching modern positions
- Ended with mass extinction
- Famous dinosaurs: T. rex, Triceratops, Velociraptor, Spinosaurus
Putting It in Perspective
- Dinosaurs: 165 million years
- Humans (Homo sapiens): ~300,000 years
- Recorded history: ~5,000 years
Dinosaurs were incredibly successful—they ruled far longer than we've existed.
Dinosaur to Dinosaur
- Stegosaurus: 155-150 million years ago
- T. rex: 68-66 million years ago
- 80+ million years apart
- Closer in time to us than to each other!
What the World Was Like
- Pangaea: Single supercontinent at start
- Gradually split into modern continents
- Different ocean currents and climate patterns
- Dinosaurs spread across all continents
- Generally warmer than today
- No polar ice caps for most of the era
- Higher CO₂ levels
- Sea levels varied significantly
- Conifers, ferns, cycads dominated early
- Flowering plants appeared in Cretaceous
- Insects, fish, mammals coexisted
- Complex food webs
Dinosaur Evolution
- Small, bipedal, quick
- Diversified after Triassic extinction
- Outcompeted other reptiles
- Thousands of species
- Every continent
- Every niche from desert to polar regions
- Huge size range
- Some evidence of declining diversity before extinction
- Still highly successful
- Extinction was sudden, not gradual
The End
- Asteroid impact
- Mass extinction
- All non-avian dinosaurs gone
- Birds survived as living dinosaurs
Why It Matters
- Reveals evolution over deep time
- Shows ecosystems can change dramatically
- Demonstrates extinction is real
- Birds carry the dinosaur legacy